Important properties in the formation of many elastomeric articles are elasticity, the maintenance of elastic properties on stretching, and softness. In the case of elastomeric gloves, and particularly thin film gloves, these properties are very important and impact on the comfort of the gloves to persons wearing them.
When a thin film glove is worn for barrier protection by a person, the gloves can become uncomfortable after a short period of time, due to fatigue associated with the resistance of the glove, which is in turn a result of an intrinsic character known as “lesser elasticity”. This property is measured in terms of its modulus (which may be measured at 500%, or preferably at 300%). It is desirable for a glove for use in such applications to have a lower modulus.
In relation to elasticity, it is often desirable in certain applications for the elastomeric article to have high elasticity properties, as indicated by a high capacity to be stretched, or elongated, before breakage. This is measured by a test that determines elongation, or more specifically, elongation at break.
It is difficult to achieve a balance of a low modulus, combined with high elongation at break, as well as desirable “feel” or touch properties, particularly without the additional potential problems that may arise through the incorporation of potential allergens. Gloves that are made from natural (polyisoprene) rubber have favourable feel and comfort properties, and can be made with a good balance between favourable modulus and elongation properties. However, natural (polyisoprene) rubber is associated with a potential allergen that causes Type I allergy. Accordingly, articles formed from synthetic elastomer alternatives having the same or improved properties compared to natural rubber are desired.
The current trend is to use nitrile rubber, (synthetic) polyisoprene rubber, polychloroprene rubber, styrene butadiene rubber, butyl rubber and/or vinyl in the production of elastomeric articles, such as gloves. These polymers are traditionally cross-linked with finely milled (solid) zinc oxide and/or sulphur cross-linking agents. Some of these materials do not provide the favourable feel and comfort of natural polyisoprene rubber. Others of the known cross-linked synthetic polymers, while having reasonable feel and comfort properties, are very expensive, making them unsuitable for the production of low cost, disposable elastomeric articles, such as gloves, condoms and the like. Although reducing the thickness (weight) of such articles made from the more expensive elastomeric polymers has been considered, reduced thickness products are at an increased risk of containing defects. The defects may be in the form of holes due to poor film formation at such fine thicknesses and/or lower endurance properties compared to the properties required by the consumer.
Elastomeric compositions have potential application in many fields, and can be used in the production of elastomeric articles other than thin film gloves (including medical gloves, surgical gloves, examination gloves) and condoms. Other examples of elastomeric articles include those for medical applications such as catheters, tubing, protective coverings, balloons for catheters and the like, and those for use in non-medical applications, such as industrial gloves, laboratory gloves, household gloves, gardening gloves, electrical gloves, irradiation gloves, finger cots, weather balloons, clean room gloves for electronic industries, gloves for food contact and food processing and biotechnical application and the like. By expanding the range of potential new elastomeric film compositions that are available, particularly low cost elastomeric article compositions, the compositions can be used in the production of a wider range of these articles, and new applications for the compositions may be developed.
In some applications and embodiments, it may also be desirable to provide new elastomeric articles, formed from new compositions, that can be produced at reduced cost. The areas for potential cost reduction may be the cost of the input components or reagents, the physical processing costs (including energy costs for performing certain production steps), and so forth.
In some applications and embodiments it may be desirable to avoid the use of reagents that have, or may have, an adverse impact on the environment.
It is an object of the present invention to provide new elastomeric articles, and compositions for the production of such articles, that provide one or more of the desired features described above.